Definition of guard cell in English:

noun

Major questions therefore remain unanswered on how water stress signals perceived at root and leaf locations are integrated at the guard cell to control stomatal behaviour.

This will reduce the apoplastic pH and allow the uptake of K + and other ions into the guard cells so that, when aquaporins are opened, water will flow into the guard cell to initiate stomatal opening.

The best documented system so far is the stomatal guard cell where two anion channels from the plasma membrane have been extensively characterized.